Hydrophobic and ice-phobic properties of self-assembled monolayers (SAMs) coatings on AA6061

• Effect of alkyl chain length on hydro/ice-phobic properties of SAM coatings was studied.
• Effect of immersion time (IT) on hydro/ice-phobic properties of the coatings was studied.
• By raising the IT, the hydrophobic properties of the coatings were enhanced.
• By raising the IT, the hydro/ice-phobic properties of the coating with longer alkyl chains were increased more.

The effects of alkyl chain length and immersion time (IT) on hydrophobic and ice-phobic properties were investigated through self-assembled monolayers of alkylsilane molecules, i.e. OT (trichloro-octylsilane) and OD (trichloro-octadecylsilane) on a flat aluminum alloy (AA6061) substrate. By increasing IT, the wetting behavior of the coatings, characterized by contact angle (CA) and contact angle hysteresis (CAH) measurements at room temperature, showed an enhancement of hydrophobic properties. However, the effect of IT on wetting properties was more significant in the case of the sample coated with longer alkyl chains (OD) than that with short alkyl chains (OT). Icing tests showed delayed ice formation and lower adhesion strength on samples with larger CA values and smaller CAH values. The scanning electron microscopy images of the coated surfaces showed the rough structure at micro/-nanometre scale on a polished aluminum surface. X-ray photoelectron spectroscopy (XPS) analysis of the coated samples showed the presence of more alkylsilane molecules when IT was increased from 15 min to 12 h.